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How to Write a Firing Schedule

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I give this tutorial to all my students when they attend class. Many tell me it has been the most helpful explanation they've ever gotten for writing firing schedules. I thought I'd share it. Hope it's helpful!
 
Firing Schedule Tutorial for Fusing
 
Firing schedules are made up of various segments and within those segments, three steps;
 
Ramp: (the rate per hour at which the kiln heats or cools). Try to think of this in terms of miles per hour. If you are traveling 300 miles and are going 50 miles an hour, it will take you 6 hours to get there. If you are ramping at 300 degrees per hour and going to 1225 degrees, it will take about 4 hours to get there. Ramp faster for small, even textured pieces and slower for thicker, larger, included and uneven pieces.
 
Temp: (the target temperature to achieve various fusing results). See below.
 
Hold: (how long the glass stays at target temperature). Gauging hold times will take some practice.
 
These are the guidelines to follow when writing fusing firing schedules. These are just general guidelines. Each step published here MIGHT be used in your firing schedule. Look at your work carefully before writing your schedule. If any of the considerations apply, write in that step; if not, skip it and move on to the next. Always consider each individual project carefully. Remember that making mistakes, while not much fun, is the best way to learn, as long as you document, retry and learn from them.
 
  1. Initial Heating: Up to 1100
    To even out the temperature through the glass and avoid thermal shock.
    To burn off materials or moisture in or around the glass. (This might require stops at lower temperatures).
    To get through the thermal shock range.

    CONSIDERATIONS: Inclusions, thickness, preheated glass, uneven surfaces, irid or dichro, position in the kiln and large pieces.

    NOTE: All these considerations require a stop at least 1100. How thick, uneven, etc. determine longer or shorter hold times. ( i.e.: the thicker the glass, the longer the hold). Remember, the goal here is to even out the temperature throughout the glass.

  2. Bubble Squeeze/Strike Colors: 1225
    To release trapped air.
    To soften glass for more even heating.
    To allow striking colors to attain target color. (Striking colors may need up to a 2-hour hold at this temperature)

    CONSIDERATIONS: Places where air can be trapped due to cutting, material placed between layers and air space purposely added for flow, striking colors.

  3. Final Heating: Rate* (see below) 1250-1400
    To get through the devitrification range. (Long holds in this range can increase chances of devitrification). 

  4. Process Stage: 1275-1700
    To reach the temperature at which the following will happen: tack fuse:1275-1400, fire polish:1300, full fuse:1450-1525 or flow:1525-1700.

    CONSIDERATIONS: Color, style of glass, viscosity of glass, uneven surface, flow, and accessories.

  5. Rapid Cooling: Rate* (see below)
    To get AFAP to annealing temperature
     
  6. Anneal: 900 (for Bullseye Glass)
    To relieve stress in the glass

    CONSIDERATIONS: Thickness, uneven surfaces, inclusions, and size. For uneven surfaces at least double your annealing times.

    Remember, you can’t over anneal your glass, but for optimal annealing, check the Bullseye chart for annealing thick slabs.

  7. Final Cooling: Rate* (Can be multiple segments)
    To gently cool the glass to room temperature and avoid thermal shock.

    CONSIDERATIONS: Thickness, uneven surfaces, inclusions, size and preheated glass

    NOTE: The thicker, more uneven, etc. require more cooling stops.

    *Rate is not a step. It is the rate at which the kiln reaches process stage, annealing or cooling temperatures.

Here is our Firing Schedule Log that we use in our studio and with all our students.



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3 comments

  • Thank you for this informative post!

    Stephanie Baness on
  • firing schedule log please!

    Beth Ulrich on
  • very good explanation but I am using Float Glass coe 82. can you tell me the schedule for that or how much to alter this schedule please?

    Terri Bunn on

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